In a conventional robot system, a safety fence physically separates an operator area which an operator can enter and a robot area in which a robot operates. However, the operator sometimes needs to enter the robot area for workpiece supply, jig or mold exchange, and the like. Physical area separation using a safety fence is easy and safe but the operator needs to unlock the key of the safety fence door to enter the robot area, which is not good for improving productivity.
Recently, there is a robot system which is known in this technical field and which includes a light curtain provided between a robot area and an operator area, and a mat switch for switching between activation and deactivation of the light curtain in order to improve productivity. Without the weight of the operator applied to the mat switch, the light curtain is deactivated and the robot arm can move to the operator area. With the weight of the operator applied to the mat switch, the light curtain is activated and the entry of the operator or the robot arm to the detection area of the light curtain stops the operation of the robot (see PTL 1, for example).
There is another robot system which is known in this technical field and in which an image-acquisition device captures the robot and the operator in an angle of view and information regarding the distance between the image-acquisition device and the imaging targets is obtained for constant monitoring of the distance between the robot and the operator (see PTL 2, for example).
There is still another robot system which is known in this technical field and which includes a plurality of floor reflective markers provided in front of the robot area, an operator reflective marker provided on the operator, an LED light source that irradiates the robot area and the floor reflective markers with light, and a photodetector that receives light reflected by each reflective marker (see PTL 3, for example).